1. Field of the Invention
This invention relates generally to electrical connectors and, more particularly, to portable apparatus that is adapted to access a field of test points for electrical testing.
2. Description of the Prior Art
Telecommunication switching systems operate on the basic principle of terminating numerous transmission facilities at a central location and then subsequently interconnecting, when required, selected pairs of facilities through a comprehensive switched network. In a telephone central office, a component of this comprehensive network is the main distribution frame which terminates outside plant facilitates and, moreover, furnishes a nonswitched interconnection juncture for joining central office equipment to the outside plant facilities.
The outside facilities homing on the central office are usually subjected to periodic tests, but aperiodic tests may also be required, particularly during troubleshooting activities for fault conditions on the facilities. In either mode, to provide efficient and reliable access for testing, main frame systems oftentimes incorporate fields of test points which are typically bridged electrically to the outside facilities terminated on the main frame. Due to the two different modes of testing, it is desirable to either (1) be able to make connections to a larger number of test points at once and to interconnect various types of test equipment, or (2) effect rapid, one-at-a-time connection to a particular test point and interconnect a variety of test instruments.
Numerous methods and devices are known in the prior art for making temporary connections to test points. These devices range: from the rudimentary type wherein a lead is soldered or an alligator-type clip is clamped to a test point; to the most complex type wherein a plurality of grip-like fingers are ganged to operate in unison via cam-lever means or a spring-loaded pin arrangement mounted with thumb screws is employed to contact many test points at once.
Two references exemplifying test connectors of the latter type are given in U.S. Pat. Nos. 3,275,971 and 3,509,297, both issued to J. H. King on September 27, 1966 and Apr. 28, 1970, respectively. These two test connectors are designed for use on conventional main frame systems that employ spring-like clamps as part of the interconnection arrangement. Conductive fingers provide electrical test access by contacting the appropriate clamps when the test apparatus is in place on the frame. Turndown screws facilitate frame mounting in '297 whereas in '971 the fingers form the primary support for frame mounting.
Presently available prior art frame access devices have been designed for conventional main frame systems. In these systems, besides the interconnection and test fields already described, a third field provides protection provisioning to safeguard personnel and equipment against excessive voltage and current. In a functional sense, the frame system provides for connection, testing and protection; and physically, in conventional frame systems, separate apparatus have served each function.
However, as elaborated upon later, the subject matter of the instant application, as well as three copending applications field on even date herewith, discloses a new modular main frame system which eliminates the independent appearance of the test field. The conventional, stand-alone test field appearance made inefficient use of available space within the central office and therefore became amenable for modification.
One component of the newly devised system is the protection device. This device, besides providing the required protection against overvoltage and overcurrent conditions, is also adapted to provide the electrical test field. Test lands, internal to the protection device, electrically contact the outside plant pairs and these lands are accessible through apertures in the protector housing. In support of the new frame arrangement, test access apparatus of an unconventional design are now required. Rather than accessing fields serving only a single purpose and best described as lug-type, clamp-like, plug- and jack-type, and so on, the apparatus must access equipment serving multipurposes. The test apparatus must be adapted to conform with the internal layout of the protector device, particularly the positioning of the flat test lands, as well as the physical dimensions and characteristics of the protector, particularly a protruding, finger grip on the housing which facilitiates handling.